Process for production of vulcanized rubber-resin composites

ABSTRACT

In the production of a vulcanized rubber-resin composite material by providing a vulcanized rubber molding in a mold, followed by injecting a resin into the mold, a vulcanizable adhesive layer containing brominated poly(2,3-dichlorobutadiene-1,3) as the main component is formed on the surface to be bonded of the vulcanized rubber molding, and then injecting the resin while keeping the vulcanizable adhesive layer to stay as formed on the surface to be bonded, thereby effecting the bonding, where a strong adhesion is established between the vulcanized rubber molding and the resin layer without any heat treatment of the vulcanized rubber molding before provision of the vulcanized rubber molding in the mold or without any heat treatment of the composite material after the resin injection.

TECHNICAL FIELD

[0001] The present invention relates to a process for producing avulcanized rubber-resin composite material and more particularly to aprocess for producing a vulcanized rubber-resin composite material witha considerably improved bonding strength.

BACKGROUND ART

[0002] Engineering plastics have distinguished characteristics such as ahigh mechanical strength, a high creep resistance, etc. and thus arewidely used in various fields as a substitute for metals. Even in thefields of industrial rubber products and automobile vibration-absorbingrubber products, formation of rubber-resin composite materials based onresins has been now in progress.

[0003] Conventional processes for producing rubber-resin compositematerials such as rubber-bushed plastic rods, bushes, engine mounts,etc. include a process, which comprises applying a rubber-based adhesiveto resin moldings, followed by vulcanization bonding to an unvulcanizedrubber, but the process suffers from such problems as occurrence ofdeformation or physical property degradation of the resin moldings dueto the mold-inside heat, a prolonged time for elevating the temperatureof resin moldings up to a necessary temperature for the vulcanizationand an inevitable production cost increase due to a longer time thanthat required for the vulcanization of metal-rubber.

[0004] As one of the processes applicable to production of theaforementioned bushed plastic rods, a process, which comprises providinga vulcanized rubber molding in a mold, followed by injection molding amolten resin into the mold (JP-B-7-55510), where the desired surface ofthe vulcanized rubber molding for bonding to the resin is subjected to atreatment according to a method (1) comprising a chlorination andapplication of a vulcanizable adhesive containing a resol type phenolresin and an aldehyde-modified polyvinyl alcohol as the main componentsor according to a method (2) comprising application of a vulcanizableadhesive containing chlorosulfonated polyethylene as the main component.

[0005] The above-mentioned method (1) suffers not only from diffusion ofan organic solvent used in the chlorination into the atmosphere and aninfluence on workers or a cost increase in fire-preventive facility,etc. due to the use of the organic solvent, but also from a fear ofdevelopment of crack generation-starting points when a shearing force isapplied to the chlorinated vulcanized rubber molding itself. The method(2) requires a heat treatment (prebaking) of the adhesive-appliedvulcanized rubber molding in advance to the injection of the moltenresin into the mold and also requires a heat treatment of thevulcanized-resin composite material after the injection. No stablequality bonding can be obtained unless such a heat treatment is carriedout fully.

DISCLOSURE OF THE INVENTION

[0006] An object of the present invention is to provide a process forproducing a vulcanized rubber-resin composite material by providing avulcanized rubber molding in a mold, followed by injecting a resin intothe mold, the process being capable of establishing a strong adhesionbetween the vulcanized rubber molding and the resin layer without anyheat treatment before the provision of the vulcanized rubber molding inthe mold or without any heat treatment of the composite material afterthe resin injection.

[0007] In the process for producing the aforementioned compositematerials, the object of the present invention can be attained byforming a vulcanizable adhesive layer containing brominatedpoly(2,3-dichlorobutadiene-1,3) as the main component on the surface tobe bonded of the vulcanized rubber molding, and then injecting the resininto the mold while keeping the vulcanizable adhesive layer to stay asformed on the surface to be bonded, thereby effecting the bonding.

[0008] The vulcanized rubber molding to be provided in the mold inadvance is at least one of vulcanized moldings of various syntheticrubbers and natural rubber, where the rubber components are notparticularly limited, but those with carbon-carbon double bonds in themolecules are preferable. Synthetic rubbers include, for example,butadiene rubber, isoprene rubber, butyl rubber, NBR, SBR, EPDM, etc.These rubber components are properly blended with a filler such ascarbon black, silica, calcium carbonate, graphite, etc., an antioxidant,a lubricant, a vulcanizing agent, a vulcanization additive, avulcanization accelerator, etc., followed by thorough kneading by theordinary kneading method and subsequently vulcanization molding in anyvulcanization mold kept ready in advance under appropriate vulcanizationconditions depending on the kind of the rubber components.

[0009] A vulcanizable adhesive containing brominatedpoly(2,3-dichlorobutadiene-1,3) as the main component, as dissolved ordispersed in an organic solvent, is applied to the surface to be bondedof the vulcanized rubber molding by any method such as brush coating,spraying, dipping, etc. to form a vulcanizable adhesive layer thereon toa thickness of about 5- about 50 μm.

[0010] Brominated poly(2,3-dichlorolbutadiene-1,3) is a well knownsubstance obtained by brominating poly(2,3-dichlorobutadiene-1,3). Forexample, Japanese Patent No. 2,927,369 (WO 95/18835) or U.S. Pat. No.5,534,591 discloses use of poly(2,3-dichlorobutadiene-1,3) containing 23wt. % Br as a film-formable component of a chlorinated polyolefinadhesive composition for bonding a metal to an elastomer material. Inthe present invention, brominated poly(2,3-dichlorobutadiene-1,3)containing about 10- about 27 wt. % Br is used, but practicallycommercially available organic solvent types, for example, Chemlock 225,a product of LOAD Co., etc. can be used as such.

[0011] Resin is injected into the mold provided with the vulcanizedrubber molding, on which a vulcanizable adhesive layer is previouslyformed by aforementioned method, and bonded thereto through thevulcanizable adhesive layer formed thereon. The resin to be injectedincludes, for example, polyamide, polyphenylene sulfide, polyethyleneterephthalate, polybutylene terephthalate, etc., and preferable for useis a polyamide resin having amide bonds in the main chain. Furthermore,to improve the mechanical strength characteristic of the resin itself, areinforcing agent such as glass fibers, carbon fibers, whiskers, etc., afiller such as carbon black, silica, calcium carbonate, etc. can beadded to the resin within such a range as not to deteriorate theprocessability, practically in a proportion of not more than about 60wt. %.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] The present invention will be described below, referring toExamples.

EXAMPLE 1

[0013] Natural rubber 100 parts by weight FEF carbon black 20 parts byweight Zink white 5 parts by weight Stearic acid 1 parts by weightPlaslicizer (naphthene series oil) 5 parts by weight Antioxidant (Nocrac3C, a product by 2.5 parts by weight Ouchi-Shinko Kagaku K. K.)Antioxidant (Nocrac 224, a product by 2.5 parts by weight Ouchi-ShinkoKagaku K. K.) Sulfur 1.5 parts by weight Vulcanization acceleralator(NOCCELER 2 parts by weight TS, a product by Ouchi-Shinko Kagaku K.K.)

[0014] A test piece in the size of 17×80×7.5 mm was made from a naturalrubber composition comprising the aforementioned blend components byvulcanization molding. The test piece was in such a shape that the upperright half portion (17×40×3 mm) was cut away.

[0015] A vulcanizable adhesive (Chemlock 225, a product by LOAD Co.)containing brominated poly(2,3-dichlorobutadiene-1,3) was applied to theto-be-bonded test piece surface corresponding to the cut-away portion,followed by providing the test piece in a mold without prebaking andinjection molding molten nylon-6,6 (filled with 50% glass fibers)therein, thereby bonding the test piece surface corresponding to thecut-away portion to the molten nylon-6,6.

EXAMPLE 2

[0016] In Example 1, molten polyethylene terephthalate (filled with 30%glass fibers) was used in place of the molten nylon-6,6 (filled with 50%glass fibers).

EXAMPLE 3

[0017] In Example 1, natural rubber/butadiene rubber (in a weight ratioof 70/30) blend rubber was used in the same amount in place of thenatural rubber.

EXAMPLE 4

[0018] In Example 1, SBR was used in the same amount in place of thenatural rubber.

COMPARATIVE EXAMPLE 1

[0019] In Example, a vulcanizable adhesive containing chlorosulfonatedpolyethylene as the main component (Chemlock 252, a product by LOAD Co.)was used.

COMPARATIVE EXAMPLE 2

[0020] In Comparative Example 1, a vulcanized molding subjected to aprebaking treatment at 120° C. for 30 minutes was used.

COMPARATIVE EXAMPLE 3

[0021] In Comparative Example 2, the resulting composite material wassubjected to a heat treatment at 120° C. for 60 minutes.

[0022] The composite materials prepared in the foregoing Examples andComparative Examples were subjected to determination of bonding strengthaccording to 90 ° peeling test procedure of JIS K-6256, determination ofrubber retention and observation of broken state. The results are shownin the following Table. TABLE Bonding strength Rubber Example (KN/m)retention (%) Broken state Example 1 14.5 100 Thick rubber layer wasretained Example 2 14.5 100 Thick rubber layer was retained Example 313.0 100 Thick rubber layer was retained Example 4 11.5 100 Thick rubberlayer was retained Comp. Ex. 1 8.5 60 Thin rubber layer was retainedComp. Ex. 2 12.3 85 Thin rubber layer was retained Comp. Ex. 3 14.2 95Thin rubber layer was retained

INDUSTRIAL APPLICABILITY

[0023] According to the present process, vulcanized rubber-resincomposite materials in firm and stable bonding between vulcanized rubbermoldings and resins can be easily produced at a low cost without such achlorination treatment or a heat treatment as in the conventionalprocess. As to the heat treatment, in the case of using a vulcanizableadhesive containing chlorosulfonated polyethylene as the main component,no satisfactory adhesion is obtained without prebaking of vulcanizedrubber moldings prior to the resin injection or without heat treatmentof the composite materials after the injection, whereas in the presentprocess vulcanized rubber-resin composite materials with satisfactoryadhesion and bonding strength can be obtained without prebaking prior tothe resin injection and without heat treatment after the resininjection.

[0024] The present process with such features can be effectively used inthe production of automobile bushes, engine mounts, etc.

1. A process for producing a vulcanized rubber-resin composite materialby providing a vulcanized rubber molding in a mold, followed byinjecting a resin into the mold, characterized by forming a vulcanizableadhesive layer containing brominated poly(2,3-dichlorobutadiene-1,3) asthe main component on the surface to be bonded of the vulcanized rubbermolding, and then injecting the resin into the mold while keeping thevulcanizable adhesive layer to stay as formed on the surface to bebonded, thereby effecting the bonding.
 2. A process for producing avulcanized rubber-resin composite material according to claim 1, whereina vulcanized molding of rubber having carbon-carbon double bonds in themolecule is used as the vulcanized rubber molding.
 3. A process forproducing a vulcanized rubber-resin composite material according toclaim 2, wherein the rubber having carbon-carbon double bonds in themolecule is natural rubber.
 4. A process for producing a vulcanizedrubber-resin composite material according to claim 2, wherein the rubberhaving carbon-carbon double bonds in the molecule is butadiene rubber,isoprene rubber, butyl rubber, NBR, SBR or EPDM.
 5. A process forproducing a vulcanized rubber-resin composite material according toclaim 1, wherein the resin to be injected is polyamide, polyphenylenesulfide, polyethylene terephthalate or polybutylene terephthalate.
 6. Aprocess for producing a vulcanized rubber-resin composite materialaccording to claim 5, wherein the resin to be injected contains afiller.
 7. A process for producing a vulcanized rubber-resin compositematerial according to claim 1, wherein neither heat treatment of thevulcanized rubber molding before provision in the mold nor heattreatment of the composite material after the resin injection is carriedout.
 8. A process for producing a vulcanized rubber-resin compositematerial according to claim 1, wherein the vulcanized rubber-resincomposite material is directed to an automobile bush or an engine mount.